[kovic]

Hey guys,

So, while i have my oil pan back off im just double checking things. And im debating on pulling my timing chain cover off again as well. (rebuild, engine on a stand)

I did the whole line the dots up, and then turn the gears to 3 oclock and 1 oclock and count 15 pins in between, and that all checked out.

I have my #1 piston at TDC, and using my old cam and sprocket and comparing it to the installed cam i realized the cam gear dot is 180 degrees out.

I turned the crank 1 rotation and that lines the dots back up. BUT, what stroke is the crank supposed to be on while dots are lined up?

Right now, if i turn the crank so that its pushing air out of the spark plug whole, once its too the top, the cam is 180 out.

Then if I rotate it while its not forcing air out of the spark plug hole the dots are lined up.

So im confused as to whether the dots need to be lined up on the compression stroke (mine are not) or on the exhaust stroke, which mine does.

Should I pull the timing chain and turn the cam 180? Do i have it on the wrong stroke.

Or am I just confused? The dots need to be lined up for distributor install right?

thanks

kov

 

[devildog80]

Dots need lined up at TDC of compression stroke, not exhaust.

Get back to TDC, pull chain and gears, and reset correctly.

 

[kovic]

Thats annoying. How was I supposed to know that when first installing the new timing chain/gears. I followed the instructions, found TDC #1 (no way to tell what stroke) then lined the dots up with the cam, Double checked it with the 15 pin count and buttoned it up....

AND just to confirm, compression stroke is when the piston is heading up putting pressure out the spark plug hole correct? BUT, if i turn the cam 180 so the dots line up, wont that just put it back to exhaust stroke since that changed the valve position?

thanks for the fast response.

kov

 

[kovic]

I found an old post by Mike Romain

"
The cam and crank gears only go in one way, with the dots lined up. You then turn the engine until the cam gear dot is about 1:00 and count the links to verify.
This install puts #1 cylinder at TDC "exhaust". It has no bearing on setting the distributor. You can rotate the engine until #1 comes back up to compression to install the distributor. "

this makes it sound like mine is fine?

kov

 

[Phil_g]

I don't see how You could if you lined up the dots and then removed the gear set, then lined the dots up on the new one. I'd turn the engine over a couple times and watch

 

[kovic]

I don't see how You could if you lined up the dots and then removed the gear set, then lined the dots up on the new one. I'd turn the engine over a couple times and watch

This is on a rebuild, so i dont really have a point of reference based on the old set.

pretty much, on every compression stroke, the cam dot is 180 out, on the exhaust stroke the dots line up.

kov

 

[Phil_g]

This is on a rebuild, so i dont really have a point of reference based on the old set.

pretty much, on every compression stroke, the cam dot is 180 out, on the exhaust stroke the dots line up.

kov

Apologies, I didn't know

 

[JEEPFELLER]

.

----JEEPFELLER

 

[keith460]

Your dots on the sprockets will align twice during the four strokes of the crank. Crank goes around 2 times vs 1 times for the cam. You must verify TDC of the crank position first with the timing chain in place. Even if the cam was out 180 degrees, no damage to the valves would occur. If you had the chain off and turned the crank, damage to valves and pistons or crank would come to a dead stop. Factory type sprockets have 18 teeth on the crank sprocket and 36 teeth on the cam sprocket. Counting the dots for 15 links works in this case but you can also get the same count if timing was put 180 degrees.
What I do is pull the #1 spark plug and install a rubber stopper in the hole. Turn the crank slowly until the rubber stopper pops out. I now know the crank is pushing the #1 piston up to TDC for the compression cycle. Slowly turn until the timing mark on the Harmonic Damper aligns with the "0" mark on the timing chain cover. We stop there and put the timing chain on and turn the cam sprocket if needed to align the dots. But I never had to rotate the cam sprocket much as we always make sure before taking it off that we are on TDC before disassembly using the rubber stopper method.

 

[JEEPFELLER]

Boss man,

when the dots are lined up----compressing is over---it's ready to fire right now!

This full downward stroke is the POWER STROKE (we're at 1/2 a turn of the crank)

As we rotate back up---we're pushing exhaust out of the exhaust manifold, we are now at 1 full turn of the crank which will put us at exhaust "TC"

(((The little gear dot is pointing to the inside----the cam dot is 180 degrees from wher we initially set it)))))

another 1/2 turn and we will have sucked in the air/fuel mix completly

as the piston starts back up this time, it is compressing the mix

when it reaches the top, the Dots line up in the center! Actually it's time for another BOOM!
x
x
the only way it could do anything else----is if the pin was swapped on the cam!

 

[JEEPFELLER]

Rethink it Keith!

2 rotations of the crank---one time with the cam!

-------JEEPFELLER

 

[keith460]

That's right. I was counting strokes as a complete revolution. It's late, brain getting muddy.

 

[kovic]

I appreciate the responses. I'm trying not to be confused. So then is mine correct?

As the piston is pushing air out of the spark plug hole the cam dot is 180 out, continue turning and as the piston is coming back up with no pressure out the spark plug hole the dots line up?

I'm racking my brain about this, I'm mean it feels like it can only go on one way, and this is a rebuild, so there was no compression or exhaust stroke when I was putting the timing chain on?

Thanks guys
Kov

 

[Fourtrail]

Yes, yours is correct. Dots line up at the beginning of 4 stroke part 1, intake, not part 3 power. Dots have nothing to do with distributor install. As said, only way to be 180 off is to swap the alignment pin in the cam end.

 

[jeepfeller_9546]

Let's make sure you are rotating the crank clockwise as viewed from the front. You are doing this by hand not with the starter correct? The dots will only line up one time in the center as you approach the dots lining up you should be compressing the air when they line up the air compression should stop.

When you removed the cam gear to begin with, did the pin fall out of the cam? If it did did you put it back in the exact hole that it came out of? That is exactly what happened to mine, but I got it straightened out, I had put the in the wrong hole. I hope this isn't even confusing you more surely you would remember if the pen fell out and you put it back in!

---imposter Jeepfeller

 

[John Strenk]

Theoretically, does it make a difference if the cam is set 180 degrees off? Just one more turn of the crank shows it's good.

Now if the crank was 180 off, that will cause problems.

 

[kovic]

Yes, yours is correct. Dots line up at the beginning of 4 stroke part 1, intake, not part 3 power. Dots have nothing to do with distributor install. As said, only way to be 180 off is to swap the alignment pin in the cam end.

Let's make sure you are rotating the crank clockwise as viewed from the front. You are doing this by hand not with the starter correct? The dots will only line up one time in the center as you approach the dots lining up you should be compressing the air when they line up the air compression should stop.

When you removed the cam gear to begin with, did the pin fall out of the cam? If it did did you put it back in the exact hole that it came out of? That is exactly what happened to mine, but I got it straightened out, I had put the in the wrong hole. I hope this isn't even confusing you more surely you would remember if the pen fell out and you put it back in!

---imposter Jeepfeller

Good stuff,. but contradicting lol. Fourtail says its correct, imposter jeepfeller says its not?

This is a rebuild, new gears, chain, cam everything. Pin never fell out. Engine is on the stand.

As the dots are getting close, there is not pressure out the spark plug hole.

Like I mentioned, but maybe it's not making sense: when the piston is on the way up and there is air pushed out, the dot is 180 out. When the piston is on the way up and no air coming out the dots line up.

I'm just trying to figure out if I need to pull the gears off a redo.

K

Im trying to understand!

k

 

[pedal2themetai]

HI , this diagram shows that the two timing marks are next to each other in a straight line for TDC to drop in the distributor (picture in the box to right), Looks like of like cam dot is at 4 o'clock and the crank dot is like at 10 o'clock..

Jeep 258 timing gear alignment - Google Search

Remember the cam turns once to two turns of the crank so one time they well line up and the next they won't..
the cam and crank sprocket only go on one way.. so if they line up as in the picture there good to go..

good luck take care be safe
tim

 

[kovic]

Thanks! Yea I did do the dot to dot and count the pins and it's all good. But I have some saying the dots come together after the compression stroke, and some like mike Romain who I quoted says they come together after exhaust stroke. Mine come together after exhaust stroke tdc.

I'm just not sure which is correct.

K

 

[rickcdewitt]

180* off isn't an issue as said before. You just roll it over to the comp cycle.don't overthink it.

Wondering about true tdc or actual cam timing? Want real info on whats going on?Get a piston stop and degree wheel.install stop and roll motor forward and backwards til it hits stop. True tdc is halfway between on degree wheel. Put at true tdc and scribe new mark on balancer.
The steps to degree a cam are easy also.google it.

If you do and find you have undesirable cam timing you can get timing sets with retarded and advanced keyways to set timing events where you want them.